Trifunctional T cell-antigen coupler and methods and uses thereof

ABSTRACT

A trifunctional molecule comprising a target-specific ligand, a ligand that binds a protein associated with the TCR complex and a T cell receptor signaling domain polypeptide is provided. Engineering T cells with this novel receptor engenders antigen specific activation of numerous T cell functions, including cytokine production, degranulation and cytolysis.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/117,173 filed on Aug. 5, 2016, now issued as of U.S. Pat. No.10,435,453 on Oct. 8, 2019, which is a national stage entry ofInternational Application No. PCT/CA2015/000068 filed on Feb. 6, 2015,which claims priority to U.S. Provisional Patent Application No.61/936,906 filed on Feb. 7, 2014, the contents of which are herebyincorporated by reference in their entirety.

FIELD

The present disclosure relates to a method of treating cancer byengineering T-cells with high cytotoxicity against specific target cellsand reduced off-target toxicity. In particular, the disclosure relatesto engineering T-cells to express novel biological agents which mimicthe natural T-cell activation process.

BACKGROUND

Cancer is a major health challenge, with over 150,000 cases of cancerexpected to be diagnosed in Canada in 2013 alone. While patients withearly stage disease can be treated effectively by conventional therapies(surgery, radiation, chemotherapy), few options are available topatients with advanced disease and those options are typicallypalliative in nature. Active immunotherapy seeks to employ the patient'simmune system to clear tumor deposits and offers an exciting option topatients who have failed conventional therapies (Humphries, 2013).Indeed, several clinical studies have demonstrated that immunotherapywith T cells can be curative in patients with advanced melanoma,confirming the utility of this approach (Humphries, 2013). Additionally,patients suffering from chronic lymphocytic leukemia (CLL) and acutelymphoblastic leukemia (ALL) have also been effectively treated andcured with T cell immunotherapy (Fry and Mackall, 2013)(Kochenderfer andRosenberg, 2013). While there are several immunotherapy approaches, theengineering of T cells with chimeric receptors allows any patient'simmune cells to be targeted against any desirable target in a majorhistocompatibility complex (MHC) independent manner. To date, thechimeric receptors used for engineering T cells consist of a targetingdomain, usually a single-chain fragment variable (scFv); a transmembranedomain; and a cytosolic domain that contains signaling elements from theT cell receptor and associated proteins (Dotti et al., 2009). Suchchimeric receptors have been referred to as “T-body”, “Chimeric AntigenReceptor” (CAR) or “Chimeric Immune Receptor” (CIR)—currently, mostresearchers use the term “CAR” (Dotti et al., 2009). These CARs areconsidered in modular terms and scientists have spent considerable timeinvestigating the influence of different cytoplasmic signaling domainson CAR function. The first-generation CARs employed a single signalingdomain from either CD3ζ or FcεRlγ. Second-generations CARs combined thesignaling domain of CD3ζ with the cytoplasmic domain of costimulatoryreceptors from either the CD28 or TNFR family of receptors (Dotti etal., 2009). Third-generation CARs combined multiple costimulatorydomains, but there is concern that third-generation CARs may loseantigen-specificity (Han et al., 2013). Most CAR-engineered T cells thatare being tested in the clinic employ second-generation CARs where CD3ζis coupled to the cytoplasmic domain of either CD28 or CD137 (Han etal., 2013)(Finney et al., 2004)(Milone et al., 2009).

While CAR-engineered T cells have shown considerable promise in clinicalapplication, they rely on a synthetic method for replacing theactivation signal that is provided by the T cell receptor (TCR). Sincethis synthetic receptor does not deliver all of the signaling componentsassociated with the TCR (ex. CD3 epsilon, Lck), it remains unclearwhether the T cells are optimally activated by the CAR or how the CARactivation affects T cell differentiation (ex. progression to memory).Furthermore, since the CAR signaling domains are disconnected from theirnatural regulatory partners by the very nature of the CAR structure,there is also an inherent risk that CARs may lead to a low-level ofconstitutive activation which could result in off-target toxicities.

Given these limitations, it is preferable to re-direct T cells to attacktumors via their natural TCR. To this end, a class of recombinantproteins termed “Bispecific T-cell Engagers” (BiTEs) has been created(Chames and Baty, 2009)(Portell et al., 2013). These proteins employbispecific antibody fragments to crosslink T-cell TCR receptors withtarget antigens. This leads to efficient T-cell activation, triggeringcytotoxicity. Similarly, bi-specific antibodies have been generated thataccomplish this goal and some scientists have simply linked anti-CD3antibodies to tumor-specific antibodies employing chemical linkage(Chames and Baty, 2009). While these bi-specific proteins havedemonstrated some activity in vitro, GMP production, short biologicalhalf-lives and bioavailability represent significant challenges to thesuccessful use of these molecules in cancer treatment. Additionally,these molecules also fail to properly recapitulate natural TCR signalingbecause they do not engage the TCR co-receptors (CD8 and CD4).

Accordingly, a need remains for T cell-antigen couplers with enhancedactivity and safety compared to traditional CARs.

SUMMARY

The present inventors have demonstrated that a trifunctional Tcell-antigen coupler that better mimics the natural signaling throughthe T cell receptor (TCR), while retaining major histocompatibilitycomplex unrestricted targeting, has enhanced activity and safetycompared to traditional chimeric antigen receptors.

Accordingly, one aspect of the disclosure provides a nucleic acidcomprising:

-   -   a. a first polynucleotide encoding a target-specific ligand;    -   b. a second polynucleotide encoding a ligand that binds a        protein associated with the TCR complex; and    -   c. a third polynucleotide encoding a T cell receptor signaling        domain polypeptide.

Another aspect of the disclosure provides a polypeptide encoded by thenucleic acid described above.

Another aspect of the disclosure provides an expression vectorcomprising the nucleic acid described above.

Yet another aspect of the disclosure provides a T-cell expressing thenucleic acid described above. Another aspect of the disclosure providesa pharmaceutical composition comprising the T cell and a carrier.

The disclosure also provides a use of a T cell for treating cancer in asubject in need thereof, wherein the T cell expresses a nucleic acidcomprising:

-   -   a. a first polynucleotide encoding a target-specific ligand;    -   b. a second polynucleotide encoding a ligand that binds a        protein associated with the TCR complex; and    -   c. a third polynucleotide encoding a T cell receptor signaling        domain polypeptide.

In one embodiment, the target-specific ligand binds an antigen on acancerous cell.

In another embodiment, the target-specific ligand is a designed ankyrinrepeat (DARPin) polypeptide or scFv.

In another embodiment, the protein associated with the TCR complex isCD3.

In another embodiment, the ligand that binds a protein associated withthe TCR complex is a single chain antibody.

In another embodiment, the ligand that binds a protein associated withthe TCR complex is UCHT1, or a variant thereof.

In another embodiment, the T cell receptor signaling domain polypeptidecomprises a cytosolic domain and a transmembrane domain.

In another embodiment, the cytosolic domain is a CD4 cytosolic domainand the transmembrane domain is a CD4 transmembrane domain.

In another embodiment the first polynucleotide and third polynucleotideare fused to the second polynucleotide.

In another embodiment, the second polynucleotide and thirdpolynucleotide are fused to the first polynucleotide.

The disclosure also provides a vector construct comprising:

-   -   a. a first polynucleotide encoding a target-specific ligand;    -   b. a second polynucleotide encoding a ligand that binds a        protein associated with the TCR complex; and    -   c. a third polynucleotide encoding a T cell receptor signaling        domain polypeptide, and    -   d. a promoter functional in a mammalian cell.

In one embodiment, the first polynucleotide and third polynucleotide arefused to the second polynucleotide to provide a T cell antigen couplerfusion and the coding sequence of the T cell antigen coupler fusion isoperably connected to the promoter.

In another embodiment, the second polynucleotide and thirdpolynucleotide are fused to the first polynucleotide to provide a T cellantigen coupler fusion and the coding sequence of the T cell antigencoupler fusion is operably connected to the promoter.

The disclosure also provides an isolated T cell transfected with thevector construct.

Other features and advantages of the present disclosure will becomeapparent from the following detailed description. It should beunderstood, however, that the detailed description and the specificexamples while indicating preferred embodiments of the disclosure aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the disclosure will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-D is a graphic summary of the trifunctional T cell-antigencoupler (Tri-TAC) in comparison with a conventional second-generationCAR. A schema of the constructs used in this work is included.

FIG. 2 shows a surface expression analysis of the Tri-TAC variants andthe classical CAR.

FIGS. 3A-B show an analysis of cell activation looking at the differentmarkers IFN-γ, TNF-α and CD107a.

FIG. 4 analyzes the killing of two different cell lines that eitherexpress (D2F2E2) or do not express (D2F2) the molecular target of theclassical CAR and the Tri-TAC.

FIGS. 5A-D depict natural T-cell initiation (5A), two currently usedartificial methods for T-cell activation (5B and 5C), and the TACactivation technology (5D).

FIGS. 6A-B depicts (6A) configuration 1 of the TAC molecule and (6B)configuration 2 of the TAC molecule.

FIGS. 7A-C show the functionality of scFv CD4 TAC. (7A) is a histogramshowing surface expression of the scFv CD4 TAC receptor relative toempty vector, (7B) shows antigen specific activation of T-cellsexpressing either the scFv CD4 TAC (top) or scFV CAR (bottom) and (7C)shows comparable killing of MCF-7 human tumour cell line (Her2 positive)by both scFv CD4 TAC and scFv CAR.

FIGS. 8A-C characterize the CD4-TAC configuration 2. (8A) is a histogramshowing surface expression of the DARPin CD4 TAC receptor relative toempty vector, (8B) shows cytokine production and degranulation of T cellengineered with DARPin TAC configuration 2 exposed to Her2 antigen and(8C) shows growth of CD4 TAC configuration 2 relative to empty vectorcontrol.

FIGS. 9A-D shows the functionality of DARPin CD4 TAC configuration 1.(9A) shows the surface expression of DARPin CD4 YAC compared to DARPinCAR and the NGFR only control, (9B) shows growth of CD4 TACconfiguration 1 and (9C) and (9D) show the percentage of cells positivefor various activation and degradation markers.

FIG. 10 shows the cytotoxicity and overall activity of TAC and CAR.Cells engineered with TAC, CAR or empty vector control were incubated invarious human tumor cell lines.

FIGS. 11A-B show receptor surface expression and activation of variousTAC controls. (11A) shows cell surface expression (left), degranulation(middle) and cytokine production (right) and (11B) shows that only fulllength CD4-TAC is able to elicit a cytotoxic response.

FIGS. 12A-C show properties of various transmembrane TAC variants. (12A)is an overview of various transmembrane domain constructs, (12B) showsthe surface of expression of various constructs engineered in CD8purified T cells and (12C) shows testing of the various variants fordegranulation and cytokine production.

FIG. 13 shows Lck interaction with TAC variants. The top panel shows theability of full length TAC and the cytosolic deletion to pull down Lckand the bottom panel is a densitometry analysis of Lck detected in thepellets of.

FIGS. 14A-B show CD4 TAC surface expression and activity compared to aBiTE like variant. (14A) depicts surface expression of an NGFR onlycontrol, CD4 TAC and BiTE like variant and (14B) compares cytotoxicityin various cell lines.

FIGS. 15A-C shows wild type CD4 TAC compared to a random mutagen libraryof UCHT1. (15A) shows the schematic representation of the mutant, (15B)is a histogram showing surface expression of the library and (15C) showsthe ability of the library to activate T cells and produce cytokines.

FIGS. 16A-C shows enhanced surface expression of the A85V, T161P mutant.(16A) compares final CD/CD8 populations between CD4 TAC and A85V, T161Pmutant, (16B) shows enhanced surface expression of the A85V, T161Pmutant and (16C) shows that cytokine production is diminished in theA85V, T161 mutant.

FIGS. 17A-B shows A85V, T161P mutant cytotoxicity and growth. (17A)shows cytotoxicity of the A85V, T161P mutant in various cell lines and(17B) shows cell growth in culture over 2 weeks.

DETAILED DESCRIPTION (i) Definitions

The term “a cell” as used herein includes a single cell as well as aplurality of cells.

The term “T cell” as used herein refers to a type of lymphocyte thatplays a central role in cell-mediated immunity. T cells, also referredto as T lymphocytes, can be distinguished from other lymphocytes, suchas B cells and natural killer cells, by the presence of a T-cellreceptor (TCR) on the cell surface. There are several subsets of T cellswith distinct functions, including but not limited to, T helper cells,cytotoxic T cells, memory T cells, regulatory T cells and natural killerT cells.

The term “T cell antigen coupler” as used herein refers to an engineerednucleic acid construct or polypeptide, that when expressed on a T cell,targets the T cell to a particular antigen.

The term “polynucleotide” and/or “nucleic acid sequence” and/or “nucleicacid” as used herein refers to a sequence of nucleoside or nucleotidemonomers consisting of bases, sugars and intersugar (backbone) linkages.The term also includes modified or substituted sequences comprisingnon-naturally occurring monomers or portions thereof. The nucleic acidsequences of the present application may be deoxyribonucleic acidsequences (DNA) or ribonucleic acid sequences (RNA) and may includenaturally occurring bases including adenine, guanine, cytosine,thymidine and uracil. The sequences may also contain modified bases.Examples of such modified bases include aza and deaza adenine, guanine,cytosine, thymidine and uracil; and xanthine and hypoxanthine. Thenucleic acids of the present disclosure may be isolated from biologicalorganisms, formed by laboratory methods of genetic recombination orobtained by chemical synthesis or other known protocols for creatingnucleic acids.

The term “isolated polynucleotide” or “isolated nucleic acid sequence”as used herein refers to a nucleic acid substantially free of cellularmaterial or culture medium when produced by recombinant DNA techniques,or chemical precursors, or other chemicals when chemically synthesized.An isolated nucleic acid is also substantially free of sequences whichnaturally flank the nucleic acid (i.e. sequences located at the 5′ and3′ ends of the nucleic acid) from which the nucleic acid is derived. Theterm “nucleic acid” is intended to include DNA and RNA and can be eitherdouble stranded or single stranded, and represents the sense orantisense strand. Further, the term “nucleic acid” includes thecomplementary nucleic acid sequences.

The term “recombinant nucleic acid” or “engineered nucleic acid” as usedherein refers to a nucleic acid or polynucleotide that is not found in abiological organism. For example, recombinant nucleic acids may beformed by laboratory methods of genetic recombination (such as molecularcloning) to create sequences that would not otherwise be found innature. Recombinant nucleic acids may also be created by chemicalsynthesis or other known protocols for creating nucleic acids.

The term “polypeptide” or “protein” as used herein describes a chain ofamino acids that correspond to those encoded by a nucleic acid. Apolypeptide or protein of this disclosure can be a peptide, whichusually describes a chain of amino acids of from two to about 30 aminoacids. The term protein as used herein also describes a chain of aminoacids having more than 30 amino acids and can be a fragment or domain ofa protein or a full length protein. Furthermore, as used herein, theterm protein can refer to a linear chain of amino acids or it can referto a chain of amino acids that has been processed and folded into afunctional protein. It is understood, however, that 30 is an arbitrarynumber with regard to distinguishing peptides and proteins and the termscan be used interchangeably for a chain of amino acids. The proteins ofthe present disclosure can be obtained by isolation and purification ofthe proteins from cells where they are produced naturally, by enzymatic(e.g., proteolytic) cleavage, and/or recombinantly by expression ofnucleic acid encoding the proteins or fragments of this disclosure. Theproteins and/or fragments of this disclosure can also be obtained bychemical synthesis or other known protocols for producing proteins andfragments.

The term “isolated polypeptide” refers to a polypeptide substantiallyfree of cellular material or culture medium when produced by recombinantDNA techniques, or chemical precursors or other chemicals whenchemically synthesized.

The term “antibody” as used herein is intended to include monoclonalantibodies, polyclonal antibodies, single chain antibodies, chimericantibodies and antibody fusions. The antibody may be from recombinantsources and/or produced in transgenic animals. The term “antibodyfragment” as used herein is intended to include without limitations Fab,Fab′, F(ab)₂, scFv, dsFv, ds-scFv, dimers, minibodies, diabodies, andmultimers thereof, multispecific antibody fragments and DomainAntibodies.

The term “vector” as used herein refers to a polynucleotide that can beused to deliver a nucleic acid to the inside of a cell. In oneembodiment, a vector is an expression vector comprising expressioncontrol sequences (for example, a promoter) operatively linked to anucleic acid to be expressed in a cell. Vectors known in the artinclude, but are not limited to, plasmids, phages, cosmids and viruses.

(ii) Compositions

The present inventors have developed a Trifunctional T cell-antigencoupler (Tri-TAC) to better mimic the natural signaling through theT-cell receptor (TCR), while retaining MHC unrestricted targeting.Specifically, the inventors created a molecule where the transmembraneand intracellular regions of the CD4 co-receptor, which localize to thelipid raft and bind Lck, respectively, were fused to single-chainantibody that binds CD3. The construct is designed to draw the CD3molecule and the TCR into regions of lipid rafts and bring Lck into theproximity of the TCR, similar to natural MHC binding. To target thechimeric receptor, a designed ankyrin repeat (DARPin) was linked to theCD4-UCHT1 chimera to generate a tri-functional T cell-antigen coupler(Tri-TAC).

Experimentally, human T cells were engineered to express either theprototype Tri-TAC or a conventional CAR with the same DARPin. It wasdetermined that in all aspects, T cells engineered with the Tri-TACdemonstrated functionality equivalent to a conventional CAR. With regardto two parameters (TNF-α production and CD107a mobilization), it wasobserved that the Tri-TAC was more active than a conventional CAR.Further, the data shows that on a per molecule basis the Tri-TAC shows asignificantly enhanced activity. Additionally the Tri-TAC offersenhanced safety compared to traditional CARs as no activation domainsare part of the protein.

Accordingly, the present disclosure relates to a nucleic acidcomprising:

a first polynucleotide encoding a target-specific ligand;

a second polynucleotide encoding a ligand that binds the TCR complex;and

a third polynucleotide encoding a T cell receptor signaling domainpolypeptide.

In one embodiment, the nucleic acid is a recombinant, or engineered,nucleic acid. In another embodiment, the first, second and/or thirdpolynucleotides are recombinant, or engineered, polynucleotides.

The disclosure also relates to a polypeptide encoded by the nucleic acidand a composition comprising the nucleic acid.

A nucleic acid comprising each of the first, second and thirdpolynucleotides, and the polypeptide encoded by the nucleic acid is alsoreferred to herein as a Trifunctional T cell-antigen coupler or Tri-TAC.

Target-Specific Ligand

The target-specific ligand directs the T cell-antigen coupler to atarget cell. Accordingly, a target-specific ligand refers to anysubstance that binds, directly or indirectly, to a target cell. A targetcell may be any cell associated with a disease state, including, but notlimited to cancer. In one embodiment, the target specific ligand bindsto an antigen (protein produced by a cell that can elicit an immuneresponse) on the target cell. The target-specific ligand can also bereferred to as an antigen binding domain.

In one embodiment, a target cell is a tumor cell. Here, atarget-specific ligand can bind to a tumor antigen or tumor associatedantigen on a tumor cell. Tumor antigens are well known in the art. Theterm “tumor antigen” or “tumor associated antigen” as used herein meansany antigenic substance produced in tumor cells that triggers an immuneresponse in a host (e.g. which can be represented by MHC complexes). Thetumor antigen when proteinaceous can for example be a sequence of 8 ormore amino acids up to the full protein and any number of amino acids inbetween 8 and the full length protein which comprises at least oneantigenic fragment of the full length protein that can be represented ina MHC complex. Examples of tumor antigens include, but are not limitedto, HER2 (erbB-2), B-cell maturation antigen (BCMA), alphafetoprotein(AFP), carcinoembryonic antigen (CEA), CA-125, MUC-1, epithelial tumorantigen (ETA), tyrosinase, melanoma-associated antigen (MAGE),prostate-specific antigen (PSA), glioma-associated antigen, (β-humanchorionic gonadotropin, thyroglobulin, RAGE-1, MN-CA IX, humantelomerase reverse transcriptase, RU1, RU2 (AS), intestinal carboxylesterase, mut hsp70-2, M-CSF, prostase, PAP, NY-ESO-1, LAGE-1a, p53,prostein, PSMA, survivin and telomerase, prostate-carcinoma tumorantigen-1 (PCTA-1), ELF2M, neutrophil elastase, CD22, insulin growthfactor (IGF)-I, IGF-II, IGF-I receptor and mesothelin.

Examples of target-specific ligands include antibodies and fragmentsthereof, for example single chain antibodies such as scFVs, or smallproteins that bind to the target cell and/or antigen.

One example of a target-specific ligand is a designed ankyrin [0063]repeat (DARPin) targeted to a specific cell and/or antigen. In oneembodiment, the target-specific ligand is a DARPin targeted to HER2(erbB-2). One example of a DARPin targeted to HER2 (erb-2) is providedherein as SEQ ID NO: 7 and 8.

Another example of a target-specific ligand is a scFV targeted to [0064]a specific cell and/or antigen. In one embodiment, the target-specificligand is a scFv that binds HER2 (erb-2). One example of an scFv thatbinds HER2 (erb-2) is provided herein as SEQ ID NO: 22 and 23.

Ligand that Binds the TCR Complex

The T cell-antigen coupler is designed to recruit the T-Cell Receptor(TCR) in combination with co-receptor stimulation. Accordingly, the Tcell antigen coupler includes a ligand that binds a protein associatedwith the T-cell receptor complex.

The TCR (T-Cell Receptor) is a complex of integral membrane proteinsthat participates in the activation of T cells in response to thebinding of an antigen. The TCR is a disulfide-linked membrane-anchoredheterodimer normally consisting of the highly variable alpha (α) andbeta (β) chains expressed as part of a complex with the invariant CD3(cluster of differentiation 3) chain molecules. T cells expressing thisreceptor are referred to as α:β (or αβ T cells, though a minority of Tcells express an alternate receptor, formed by variable gamma (γ) anddelta (δ) chains, referred as γδ T cells. CD3 is a protein complexcomposed of four distinct chains. In mammals, the complex contains aCD3γ chain, a CD3δ chain, and two CD3ε chains.

As used herein, the term “ligand that binds a protein associated withthe T-cell receptor complex” includes any substance that binds, directlyor indirectly, to a protein of the TCR. Proteins associated with the TCRinclude, but are not limited to the TCR alpha (α) chain, TCR beta (β)chain, TCR gamma (γ) chain, TCR delta (δ) chain, CD3γ chain, CD3δ chainand CD3ε chains. In one embodiment, a ligand that binds a proteinassociated with the T-cell receptor complex is an antibody to the TCRalpha (α) chain, TCR beta (β) chain, TCR gamma (γ) chain, TCR delta (δ)chain, CD3γ chain, CD3δ chain and/or CD3E chain.

In one embodiment, the ligand is an antibody or a fragment thereof thatbinds CD3. Examples of CD3 antibodies are known in the art (formuromonab, otelixizumab, teplizumab and visilizumab). In one embodiment,the antibody that binds CD3 is a single chain antibody, for example asinglechain variable fragment (scFv).

Another example of a CD3 antibody is UCHT1 which targets CD3ε. Asequence for UCHT1 is provided herein as SEQ ID NOs: 13 and 14.

T Cell Receptor Signaling Domain Polypeptide

The T cell antigen coupler includes a T cell receptor signaling domainpolypeptide. As used herein, the term “T cell receptor signaling domain”refers to a polypeptide that (a) localizes to the lipid raft and/or (b)binds Lck. A T cell receptor signaling domain polypeptide can includeone or more protein domains including, but not limited to, a cytoplasmicdomain and/or a transmembrane domain. As used herein, “protein domain”refers to a conserved part of a given protein sequence structure thatcan function and exist independently of the rest of the protein chain.In one embodiment, the T cell receptor signaling domain polypeptideincludes a cytoplasmic domain. In another embodiment, the T cellreceptor signaling domain polypeptide includes a transmembrane domain.In a further embodiment, the T cell receptor signaling domainpolypeptide includes both a cytoplasmic and a transmembrane domain.

T cell receptor signaling domain polypeptides include TCR co-receptorsand co-stimulators and TCR co-receptor and co-stimulator proteindomains.

A “TCR co-receptor” refers to a molecule that assists the T cellreceptor (TCR) in communicating with an antigen-presenting cell.Examples of TCR co-receptors include, but are not limited to, CD4, CD8,CD28, CD45, CD4, CD5, CDS, CD9, CD16, CD22, CD33, CD37, CD64, CD80,CD86, CD134, CDt 37 and CD 154.

A “TCR co-stimulator” refers to a molecule that is required for theresponse of a T cell to an antigen. Examples of TCR co-stimulatorsinclude, but are not limited to, PD-1, ICOS, CD27, CD28, 4-1BB (CD 137),OX40, CD30, 25 CD40, lymphocyte fiction-associated antigen 1 (LFA-1),CD2, CD7, LIGHT, NKG2C, B7-H3, and a ligand that specifically bindsCD83.

In one embodiment, the T cell receptor signaling domain polypeptideincludes both a cytoplasmic domain and a transmembrane domain of a TCRco-receptor or co-stimulator protein. The cytoplasmic domain andtransmembrane domain may be from the same co-receptor or co-stimulatoror from different co-receptors or co-stimulators. The cytoplasmic domainand transmembrane domains are optionally joined by a linker.

In one embodiment, the T cell receptor signaling domain polypeptidecomprises the transmembrane and cytoplasmic domains of the CD4co-receptor (see for example SEQ ID NO: 17 and 18).

In another embodiment, the T cell receptor signaling domain polypeptidecomprises the transmembrane and cytoplasmic domains of the CD8aco-receptor.

In other embodiment, the cytoplasmic and/or transmembrane domain of theT cell receptor signaling domain polypeptide is synthetic. For example,the transmembrane domain is optionally a synthetic, highly hydrophobicmembrane domain.

In another example, the transmembrane domain is a glycophorinetransmembrane domain. In yet another example the T cell receptorsignaling domain polypeptide includes a CD48 GPI signal sequence toattach the T-cell antigen coupler to the membrane using the GPI anchor.

In addition to the three components of the T cell antigen couplerdescribed herein (target-specific ligand, ligand that binds the TCRcomplex and T cell receptor signaling domain polypeptide), it iscontemplated that other polypeptides could also be included. Forexample, the T cell antigen coupler optionally includes additionalpolypeptides that directly or indirectly act to target or activate the Tcell.

Linkers

The various components of the T cell antigen coupler can be fuseddirectly to each other, or they may be joined by at least one linker,optionally a peptide linker. The peptide linker can be of any sizeprovided it does not interfere with the function of the individuallinked components. In one embodiment, the peptide linker is from about 1to about 15 amino acids in length, more specifically from about 1 toabout 10 amino acids, and most specifically from about 1 to about 6amino acids.

Examples of linkers useful in the T cell antigen coupler include theG4S3 linker. Other examples of linkers are peptides corresponding to SEQID NOs: 11, 12, 15, 16, 19, 20 and 21 and variants and fragmentsthereof:

Configuration

The T cell-antigen coupler may be present in various configurations aswill be readily appreciated by a person of skill in the art.

In one embodiment, the target specific ligand and the T cell receptorsignaling domain polypeptide are both fused to the ligand that binds theTCR complex. For example, the N-DARPin TAG described here (also referredto as configuration 1; SEQ ID NO: 1 and 2) includes, in order:

i) N-Darpin Tri TAG leader sequence (secretion signal) (SEQ ID NO: 5 and6)

ii) DARPin specific for Her2 antigen (SEQ ID NO: 7 and 8)

iii) Myc tag (SEQ ID NO: 9 and 10)

iv) Linker 1 (SEQ ID NO: 11 and 12)

v) UCHT1 (SEQ ID NO: 13 and 14)

vi) Linker 2 (SEQ ID NO: 15 and 16)

vii) CD4 (SEQ ID NO: 17 and 18)

In another embodiment, the DARPin is replaced with a scFV ScFv specificfor a Her2 antigen (SEQ ID NO: 22 and 23).

In another embodiment, the ligand that binds the TCR complex and the Tcell receptor signaling domain polypeptide are both fused to the targetspecific ligand (C-DARPin TAG as described here (also referred to asconfiguration 1; SEQ ID NO: 3 and 4)). Alternative configurations willbe readily apparent to a person of skill in the art.

Vector Constructs

A variety of delivery vectors and expression vehicles can be employed tointroduce nucleic acids described herein into a cell. Accordingly, theaforementioned polynucleotides are optionally comprised in a vector toprovide a vector construct, also herein referred to as a vector.

Therefore, the present disclosure also relates to a vector comprising:

a. a first polynucleotide encoding a target-specific ligand;

b. a second polynucleotide encoding an antibody that binds CD3; and

c. a third polynucleotide encoding a T cell receptor signaling domainpolypeptide, and optionally a promoter functional in a mammalian cell.

Promoters, regions of DNA that initiate transcription of a particularnucleic acid sequence, are well known in the art. A “promoter functionalin a mammalian cell” refers to a promoter that drives expression of theassociated nucleic acid sequence in a mammalian cell. A promoter thatdrives expression of a nucleic acid sequence may be referred to as being“operably connected” to the nucleic acid sequence.

In one embodiment, the first polynucleotide and third polynucleotide arefused to the second polynucleotide to provide a T cell antigen couplerfusion and the coding sequence of the T cell antigen coupler fusion isoperably connected to the promoter.

In another embodiment, the second polynucleotide and thirdpolynucleotide are fused to the first polynucleotide to provide a T cellantigen coupler fusion and the coding sequence of the T cell antigencoupler fusion is operably connected to the promoter.

Optionally, the vector is designed for expression in mammalian cellssuch as T cells. In one embodiment, the vector is a viral vector,optionally a retroviral vector.

Vectors that are useful comprise vectors derived from lentiviruses,Murine Stem Cell Viruses (MSCV), pox viruses, oncoretroviruses,adenoviruses, and adeno-associated viruses. Other delivery vectors thatare useful comprise vectors derived from herpes simplex viruses,transposons, vaccinia viruses, human papilloma virus, Simianimmunodeficiency viruses, HTLV, human foamy virus and variants thereof.Further vectors that are useful comprise vectors derived fromspumaviruses, mammalian type B retroviruses, mammalian type Cretroviruses, avian type C retroviruses, mammalian type D retrovirusesand HTLV/BLV type retroviruses. One example of a lentiviral vectoruseful in the disclosed compositions and methods is the pCCL vector.

Variations of Polynucleotides and Polypeptides

Many modifications may be made to the polynucleotide sequences includingvector sequences and polypeptides sequences disclosed in thisapplication and these will be apparent to one skilled in the art.Modifications include substitution, insertion or deletion of nucleotidesor amino acids or altering the relative positions or order ofnucleotides or amino acids.

In one embodiment, the polynucleotides described herein may be modifiedor mutated to optimize the function of the encoded polypeptide and/orthe function, activity and/or expression of the T cell antigen coupler.

It is shown herein that UCHT1 mutant can be generated that results inenhanced surface expression of the TAG (FIGS. 15-17). Accordingly, inone embodiment, the TAG comprises a modified or mutated ligand thatbinds the TCR complex, wherein the TAG comprising the modified ormutated antibody has increased surface expression and/or activitycompared to a TAG comprising a wild type, or non-modified or mutatedligand that binds the TCR complex. An example of a mutated or modifiedantibody that binds CD3 is the UCHT1 A85V, T161P mutant described herein(SEQ ID NO: 24 and 25).

Sequence Identity

The polynucleotides of the application also include nucleic acidmolecules (or a fragment thereof) having at least about: 70% identity,at least 80% identity, at least 90% identity, at least 95% identity, atleast 96% identity, at least 97% identity, at least 98% identity or, atleast 99% or 99.5% identity to a nucleic acid molecule of theapplication. The polypeptides of the application also includepolypeptides (or a fragment thereof) having at least about: 70%identity, at least 80% identity, at least 90% identity, at least 95%identity, at least 96% identity, at least 97% identity, at least 98%identity or, at least 99% or 99.5% identity to a polypeptide of theapplication. Identity refers to the similarity of two nucleotide orpolypeptide sequences that are aligned so that the highest order matchis obtained. Identity is calculated according to methods known in theart. For example, if a nucleotide sequence (called “Sequence A”) has 90%identity to a portion of SEQ ID NO: 1, then Sequence A will be identicalto the referenced portion of SEQ ID NO: 1 except that Sequence A mayinclude up to 10 point mutations (such as substitutions with othernucleotides) per each 100 nucleotides of the referenced portion of SEQID NO:

Sequence identity is preferably set at least about: 70% identity, atleast 80% identity, at least 90% identity, at least 95% identity, atleast 96% identity, at least 97% identity, at least 98% identity or,most preferred, at least 99% or 99.5% identity to the nucleotidesequences provided herein and/or its complementary sequence. Sequenceidentity is also preferably set at least about: 70% identity, at least80% identity, at least 90% identity, at least 95% identity, at least 96%identity, at least 97% identity, at least 98% identity or, mostpreferred, at least 99% or 99.5% identity to the polypeptide sequencesprovided herein. Sequence identity will preferably be calculated withthe GCG program from Bioinformatics (University of Wisconsin). Otherprograms are also available to calculate sequence identity, such as theClustal W program (preferably using default parameters; Thompson, J D etal., Nucleic Acid Res. 22:4673-4680).

Hybridization

The application includes DNA that has a sequence with sufficientidentity to a nucleic acid molecule described in this application tohybridize under stringent hybridization conditions (hybridizationtechniques are well known in the art). The present application alsoincludes nucleic acid molecules that hybridize to one or more of thesequences described herein and/or its complementary sequence. Suchnucleic acid molecules preferably hybridize under high stringencyconditions (see Sambrook et al. Molecular Cloning: A Laboratory Manual,Most Recent Edition, Cold Spring Harbor Laboratory Press, Cold SpringHarbor, N.Y.). High stringency washes have preferably have low salt(preferably about 0.2% SSC) and a temperature of about 50-65° C. and areoptionally conducted for about 15 minutes.

Expression in T cells

The T cell antigen coupler is designed for expression in T cells.Accordingly, one aspect of the disclosure provides a T cell expressing aT cell antigen coupler. Another aspect of the disclosure relates to a Tcell transduced or transfected with T cell antigen coupler or a vectorcomprising a T cell antigen coupler. Optionally, the T cell is anisolated T cell.

T cells can be obtained from a number of sources, including, but notlimited to blood (for example, peripheral blood mononuclear cells), bonemarrow, thymus tissue, lymph node tissue, cord blood, thymus tissue,tissue from an infection site, spleen tissue, and tumors. In oneembodiment, the T cells are autologous T cells. In another embodiment,the T cells are obtained from a cell line of T cells. Methods ofculturing and maintaining T cells in vitro are well known in the art.

Once obtained, the T cells are optionally enriched in vitro. As is wellknown in the art, a population of cells can be enriched by positive ornegative selection. Further, the T cells can be optionally frozen orcryopreserved and then thawed at a later date.

Before or after introducing the T cell antigen coupler to the T cells,the T cells are optionally activated and/or expanded using methods wellknown in the art. For example, the T cells can be expanded by contactwith a surface having attached thereto an agent that stimulates aCD3/TCR complex associated signal and a ligand that stimulates aco-stimulator molecule on the surface of the T cells.

Methods of transducing or transfecting T cells with nucleic acidsequences and expressing the transduced nucleic acids in the T cells arewell known in the art. For example, a nucleic acid can be introducedinto a cell by physical, chemical or biological means. Physical meansinclude, but are not limited to, (microinjection, electroporation,particle bombardment, lipofection and calcium phosphate precipitation).Biological means include the use of DNA and RNA vectors.

In one embodiment, viral vectors, including retroviral vectors, are usedto introduce and express a nucleic acid into a T cell. Viral vectorsinclude vectors derived from lentivirus, Murine Stem Cell Viruses(MSCV), pox viruses, herpes simplex virus I adenovirus andadeno-associated viruses. The vector optionally includes a promoter thatdrives expression of the transduced nucleic acid molecule in a T cell.

Various assays may be used to confirm the presence and/or expression ofthe transduced nucleic acid sequence and/or the polypeptide encoded bythe nucleic acid in the T cell. Assays include, but are not limited toSouthern and Northern blotting, RT-PCR and PCR, ELISAs and Westernblotting.

In one embodiment, a T cell expressing a T cell antigen coupler hasincreased T cell activation in the presence of an antigen compared to aT cell not expressing a T cell antigen coupler and/or as compared to a Tcell expressing a traditional CAR. Increased T cell activation can beascertained by numerous methods, including but not limited to, increasedtumor cell line killing, increased cytokine production, increasedcytolysis, increased degranulation and/or increased expression ofactivation markers such as CD107α, IFNγ, II-2 or TNFα. Increases may bemeasured in an individual cell or in a population of cells.

The terms “increased” or “increasing” as used herein refer to at least a2%, 5%, 10%, 25%, 50%, 100% or 200% increase in a T cell or populationof T cells expressing a T cell antigen coupler compared to a T cell orpopulation of T cells not expressing a T cell antigen coupler and/or ascompared to a T cell or population of T cells expressing a traditionalCAR.

T cells, optionally autologous T cells, expressing the T cell antigencoupler can be administered to a subject in need thereof. According, a Tcell transduced with and/or expressing a T cell antigen coupler can beformulated in a pharmaceutical composition. Preferably, the T cells areformulated for intravenous administration.

A pharmaceutical composition can be prepared by per se known methods forthe preparation of pharmaceutically acceptable compositions that can beadministered to subjects, such that an effective quantity of the T cellsare combined in a mixture with a pharmaceutically acceptable carrier.Suitable carriers are described, for example, in Remington'sPharmaceutical Sciences (Remington's Pharmaceutical Sciences, 20th ed.,Mack Publishing Company, Easton, Pa., USA, 2000). On this basis, thecompositions include, albeit not exclusively, solutions of thesubstances in association with one or more pharmaceutically acceptablecarriers or diluents, and contained in buffered solutions with asuitable pH and iso-osmotic with the physiological fluids.

Suitable pharmaceutically acceptable carriers include essentiallychemically inert and nontoxic compositions that do not interfere withthe effectiveness of the biological activity of the pharmaceuticalcomposition. Examples of suitable pharmaceutical carriers include, butare not limited to, water, saline solutions, glycerol solutions,ethanol, N-(1(2,3-dioleyloxy)propyl)N,N,N-trimethylammonium chloride(DOTMA), diolesylphosphotidyl-ethanolamine (DOPE), and liposomes. Suchcompositions should contain a therapeutically effective amount of thecompound, together with a suitable amount of carrier so as to providethe form for direct administration to the patient.

Pharmaceutical compositions may also include, without limitation,lyophilized powders or aqueous or non-aqueous sterile injectablesolutions or suspensions, which may further contain antioxidants,buffers, bacteriostats and solutes that render the compositionssubstantially compatible with the tissues or the blood of an intendedrecipient. Other components that may be present in such compositionsinclude water, surfactants (such as Tween), alcohols, polyols, glycerinand vegetable oils, for example. Extemporaneous injection solutions andsuspensions may be prepared from sterile powders, granules, tablets, orconcentrated solutions or suspensions.

(iii) Methods and Uses

One aspect of the present disclosure provides the use of a TrifunctionalT-cell antigen coupler to direct a T cell to a specific antigen.

Accordingly, the present disclosure also relates to the use of amodified T cell for treating cancer in a subject in need thereof,wherein the modified T cell expresses a nucleic acid comprising a firstpolynucleotide encoding a target-specific ligand, a secondpolynucleotide encoding an ligand that binds the TCR complex; and athird polynucleotide encoding a T cell receptor signaling domainpolypeptide. The disclosure also relates to methods for treating cancer,comprising administering an effective amount of modified T cells to asubject in need thereof. Also disclosed is use of an effective amount ofmodified T cells for treating cancer in a subject in need thereof.Further disclosed is use of a modified T cell in the preparation of amedicament treating cancer in a subject in need thereof. Even furtherdisclosed is a modified T cell for use in treating cancer in a subjectin need thereof. In one embodiment, the target-specific ligand binds anantigen on a cancerous cell, thereby targeting the modified T cell tothe cancerous cell.

Cancers that may be treated include any form of neoplastic disease.Examples of cancers that may be treated include, but are not limited tobreast cancer, lung cancer and leukemia, for example mixed lineageleukemia (MLL), chronic lymphocytic leukemia (CLL) or acutelymphoblastic leukemia (ALL). Other cancers include carcinomas,blastomas, melonomas, sarcomas, hematological cancers, lymphoidmalignancies, benign and malignant tumors, and malignancies. The cancercan comprise non-solid tumors or solid tumors. Cancers that may betreated include tumors that are not vascularized, or not yetsubstantially vascularized, as well as vascularized tumors.

The modified T cells and/or pharmaceutical compositions described hereinmay be administered to, or used in, living organisms including humans,and animals. The term “subject” as used herein refers to any member ofthe animal kingdom, preferably a mammal, more preferably a human being.

Procedures for isolating, genetically modifying, and administering Tcells to a subject in need thereof are known in the art. In particular,T cells are isolated from a mammal (preferably a human), optionallyexpanded and/or activated as described herein and transduced ortransfected with the nucleic acid molecules of the disclosure. The Tcells can be autologous with respect to the subject. In anotherembodiment, the cells can be allogeneic, syngeneic or xenogeneic withrespect to the subject.

The modified T cells can be administered either alone, or as apharmaceutical composition, as described herein. Compositions of thepresent disclosure are preferably formulated for intravenousadministration.

Administration of an “effective amount” of the modified T cells and/orpharmaceutical compositions is defined as an amount effective, atdosages and′ for periods of time necessary to achieve the desiredresult. For example, an effective amount of a substance may varyaccording to factors such as the disease state, age, sex, and weight ofthe individual, and the ability of the recombinant protein to elicit adesired response in the individual. Dosage regime may be adjusted toprovide the optimum therapeutic response. For example, several divideddoses may be administered daily or the dose may be proportionallyreduced as indicated by the exigencies of the therapeutic situation.

For example, the modified T cells and/or pharmaceutical compositionsdescribed herein may be administered at a dosage of 10⁴ to 10⁹ cells perkg body weight, optionally 10⁵ to 10⁸ cells per kg body weight or 10⁶ to10⁷ cells per kg body weight. The dosage can be administered a singletime or multiple times.

The modified T cells and/or pharmaceutical compositions may beadministered by any method known in the art, including but not limitedto, aerosol inhalation, injection, ingestion, transfusion, implantationor transplantation. The modified T cells and/or pharmaceuticalcompositions may administered to a subject subcutaneously,intradennally, intratumorally, intranodally, intrameduliary,intramuscularly, by intravenous (i.v.) injection, or intraperitoneally.The modified T cells and/or pharmaceutical compositions thereof may beinjected directly into a tumor, lymph node, or site of infection.

As used herein, and as well understood in the art, “to treat” or“treatment” is an approach for obtaining beneficial or desired results,including clinical results. Beneficial or desired clinical results caninclude, but are not limited to, alleviation or amelioration of one ormore symptoms or conditions, diminishment of extent of disease,stabilized (i.e. not worsening) state of disease, preventing spread ofdisease, delay or slowing of disease progression, amelioration orpalliation of the disease state, and remission (whether partial ortotal), whether detectable or undetectable. “Treatment” can also meanprolonging survival as compared to expected survival if not receivingtreatment. In one embodiment, “treatment” includes preventing a diseaseor condition.

Nucleotide/Amino SEQ ID NO Description Acid SEQ ID NO: 1 N-Darpin TriTAC Nucleotide SEQ ID NO: 2 N-Darpin Tri TAC Amino Acid SEQ ID NO: 3C-Darpin Tri TAC Nucleotide SEQ ID NO: 4 C-Darpin Tri TAC Amino Acid SEQID NO: 5 N-Darpin Tri TAC leader Nucleotide sequence (secretion signal)SEQ ID NO: 6 N-Darpin Tri TAC leader Amino Acid sequence (secretionsignal) SEQ ID NO: 7 DARPin specific for Her2 Nucleotide antigen SEQ IDNO: 8 DARPin specific for Her2 Amino Acid antigen SEQ ID NO: 9 Myc TagNucleotide SEQ ID NO: 10 Myc Tag Amino Acid SEQ ID NO: 11 Linker 1Nucleotide SEQ ID NO: 12 Linker 1 Amino Acid SEQ ID NO: 13 UCHT1¹Nucleotide SEQ ID NO: 14 UCHT1² Amino Acid SEQ ID NO: 15 Linker 2Nucleotide SEQ ID NO: 16 Linker 2 Amino Acid SEQ ID NO: 17 CD4 Domain³Nucleotide SEQ ID NO: 18 CD4 Domain⁴ Amino Acid SEQ ID NO: 19 Universalrigid linker Amino Acid SEQ ID NO: 20 CD28 based linker Amino Acid SEQID NO: 21 CD4 based linker Amino Acid SEQ ID NO: 22 ScFv specific forHer2 antigen Nucleotide SEQ ID NO: 23 ScFv specific for Her2 antigenAmino Acid SEQ ID NO: 24 UCHT1 (A85V, T161P) Nucleotide SEQ ID NO: 25UCHT1 (A85V, T161P) Amino Acid ¹Light chain, nucleotides 1-324; Linker,nucleotides 325-387; Heavy chain, nucleotides 388-750 ²Light chain,amino acids 1-108; Linker, amino acids 109-128; Heavy chain, amino acids129-250 ³Extracellular linker, nucleotides 1-66; Transmembrane domain,nucleotides 67-132; Cytosolic domain, nucleotides 133-254 ⁴Extracellularlinker, amino acids 1-22; Transmembrane domain, amino acids 23-44;Cytosolic domain, amino acids 45-84

The above disclosure generally describes the present application. A morecomplete understanding can be obtained by reference to the followingspecific examples. These examples are described solely for the purposeof illustration and are not intended to limit the scope of theapplication. Changes in form and substitution of equivalents arecontemplated as circumstances might suggest or render expedient.Although specific terms have been employed herein, such terms areintended in a descriptive sense and not for purposes of limitation.

The following non-limiting examples are illustrative of the presentapplication.

EXAMPLES Example 1

Background and Summary

A trifunctional T cell-antigen coupler (Tri-TAC) was developed to betterrecapitulate the natural signaling through the TCR, while retaining MHCunrestricted targeting. T-cell activation occurs following ligation ofMHC by the TCR and co-receptor on the T cells (either CD4 or CD8)simultaneously bind to conserved regions within the MHC molecule (Yin etal., 2012)(Kuhns and Davis, 2012). The co-receptors are specificallylocated within “lipid rafts” (Fragoso et al., 2003XArcaro et al., 2000),membrane micro domains that are particularly important for TCR signalcomplex formation (He and Marguet, 2008). In addition to ensuring thecorrect microdomain localization of the TCR activation complex, theseco-receptors also bind directly to Lck (Kim et al., 2003), a proteinkinase that is crucial for T-cell activation (Methi et al., 2005)(Acutoand Cantrell, 2000). As stated previously, none of the existing chimericreceptors or bi-functional proteins engage the co-receptor molecules orLck. A molecule was created where the transmembrane and intracellularregions of the CD4 co-receptor, which localize to the lipid raft andbind Lck, respectively, were fused to single-chain antibody that bindsCD3 (UCHT1; SEQ ID NO: 13 and 14; sequence is also in the publicdomain). This construct is designed to draw the CD3 molecule and the TCRinto regions of lipid rafts and bring Lck into the proximity of the TCR,similar to natural MHC binding. To target this chimeric receptor, adesigned ankyrin repeat (DARPin) was linked to the CD4-UCHT1 chimera togenerate a tri-functional T cell-antigen coupler (Tri-TAC). In thisspecific case, the DARPin was specific for the proto-oncogene, erbB-2.

Human T cells were engineered to express either the prototype Tri-TAC ora conventional CAR with the same DARPin. It was determined that in allaspects, T cells engineered with the Tri-TAC demonstrated functionalityequivalent to a conventional CAR. Interestingly, with regard to 2parameters (TNF-α production and CD107a mobilization), it was observedthat the Tri-TAC was more active than a conventional CAR. Further, thedata shows that on a per molecule basis the Tri-TAC shows asignificantly enhanced activity. Additionally the Tri-TAC offersenhanced safety compared to traditional CARs as no activation domainsare part of the protein.

The traditional CAR is effective in stimulating T-cells by combiningseveral signaling domains (FIG. 1C). By comparison, the Tri-TAC (FIG. 1A/B) does not contain any signaling domains of its own. It relies purelyon facilitating the proposed interactions between other key players(shown in grey) in an antigen dependent manner. To test this designhypothesis, several variants of the full length N-Darpin Tri-TAC weregenerated (FIG. 1D).

Previous work has established the consistent and significant cellsurface expression of CAR molecules. It was found that the Darpin CARshows robust surface expression (FIG. 2). In contrast, Tri-TAC showed amuch lower surface expression. This was observed for all variants thathad the UCHT1 domain. However, the Tri-TAC variant lacking the UCHT1domain showed surface expression similar to the Darpin CAR.

T cells engineered to express the Tri-TAC, the Tri-TAC variants or The Tcells the DARPin CAR were stimulated with plate-bound antigen,engineered to express the Tri-TAC and DARPin CAR could elaborate allmeasured functions (TNF-α production, IFN-γ production and CD107amobilization) (FIGS. 3A and 3B). Binding of the Tri-TAC to both CD3 andthe target antigen was found to be critical for the T cells to elaboratetheir functions. In FIG. 3, it is demonstrated that removal of UCHT1,which abolishes binding to CD3, abrogates the function of the Tri-TAC.In other data, it was determined that removal of the DARPin from theTri-TAC also abrogates function.

As expected, when these T-cells were tested for their cytotoxicity,Tri-TAC-UCHT1-Darpin showed no ability to kill antigen expressing cells(FIG. 4). N-Darpin Tri-TAC showed a high level of selective cytotoxicitythat was very similar to the classical DARPin-CAR. Interestingly, the Tcells expressing the DARPin-CAR appear to display off-target killing athigh T-cell:target cell ratios (see killing on D2F2 in FIG. 4) whereasthe T cells expressing the Tri-TAC did not display these effects.

EXPERIMENTAL

FIG. 1 is a schematic overview. (A) Depicts N-Darpin Tri-TAC. Theankyrin repeat domain targeted against Her2 is fused to the single chainfragment variable (scFv) UCHT1 using a (G4S)₃ linker. The scFv is thenlinked to the CD4 molecule. The CD4 contains the linker region andtransmembrane region as well as the cytoplasmic anchoring region.Potential interactions are shown in faded gray. (B) Depicts the C-DarpinTri-TAC. In this construct, the scFv UCHT1 is switched with the Darpindomain. Potential interactions are again depicted in faded gray. (C)Model of a classical second generation CAR. The Darpin targeting domainis linked via a CD8a linker to the CD28 transmembrane domain. The CD3zeta domain with its 3 activating ITAM motifs is then connected to thecytosolic portion of CD28. (D) Overview of the various Tri-TAC controls,lacking either the Darpin targeting domain, the CD3 binding scFv moiety,or the cytosolic portion of the CD4 domain.

FIG. 2 shows the phenotypic surface expression analysis of transducedT-cells with histograms of respective Tri-TAC variants. T-cells had beenincubated with Her2Fc, which later was detected via flow cytometry. Thepresented data was gated on CD8+ lymphocytes. The shown gates werechosen based on the untransduced control.

FIG. 3 is a functional analysis of engineered T-cells. In (A), cellswere stimulated for 4 hours with plate bound Her2Fc in media containingGolgiPlug™. Cells were first stained for CD8+, then permeabilized andanalyzed for TNF-α and IFN-γ production. Initial gates were set forsinglet CD8+ lymphocytes. The shown gates were set based on theuntransduced control. In B), as before, cells were stimulated with platebound Her2Fc. Media included GolgiPlug™ as well as an anti-CD107aantibody. Actively degranulating cells were expected to have a higherrate of CD107a recycling, and subsequently show a higher signal foranti-CD107α.

FIG. 4 shows engineered T-cell cytotoxicity. Two different adherentmouse tumor lines were plated 24 hours prior to T-cell addition. D2F2/E2have been engineered to express human Her2, whereas the D2F2 do not.Indicated ratios of T-cells were added to tumor containing wells. Tumorcells were incubated for 6h with T-cells. T-cells were subsequentlyremoved via washing. 10% Alamar blue containing media was added to eachwell for 3 hours. The metabolic activity, as an indicator of cellsurvival, was determined via endpoint analysis. Wells without T-cellswere defined as maximum survivability/metabolic activity and set to100%, whereas media incubated without cells was set as 0% metabolicactivity. Data presented is the average of 3 replicates.

DISCUSSION

Using chimeric receptors to redirect T-cells towards specific targets inan MHC-independent manner is an attractive method to treat cancer andmay be applicable to infectious diseases where antigens from thepathogen are found on the plasma membrane. The chimeric receptor wouldresult in: (1) specific cytotoxicity against the target cells and (2)minimal off target toxicity. Conventional CARs are limited in thisregard because they rely upon a synthetic structure where signalingdomains are located in unnatural positions where they may not receiveproper regulation and, thus, there is reduced cellular control ofspecific activity.

The Tri-TAC was designed to re-direct the signaling components of thenatural TCR without employing ectopic localization of signaling domains.The Tri-TAC was designed with the following principles: (1) the chimericreceptor should interact and facilitate ordered assembly of keyactivating protein complexes, (2) the chimeric receptor should takeadvantage of preexisting cellular adaptations, such as micro-domainenvironments and (3) the chimeric receptor should not possess anyactivating domains. The Tri-TAC is able to achieve this efficiently and,as the data demonstrates, at rates of activation that are equal to, ifnot better than, that of a 2nd generation CAR.

This Tri-TAC is thus ideally suited for further integration withadditional designed co-receptors to further fine tune T-cell activation.Ultimately this should lead to much reduced off target effects withoutcompromising on targeted cytotoxicity. Tri-TAC appears to exhibit lowertoxicity than existing CARs. Darpin CARs show mild off target killing athigh cell to target ratios, which may become problematic when used intherapies. However, Tri-TAC, which is as functional as the traditionalCAR, did not display off-target effects. Since DARPins bind targets withhigh affinity, off-target effects may be more common on cells thatexpress high levels of a chimeric receptor that employs a DARPin.Therefore, without being bound by theory, the low surface expression ofthe Tri-TAC may be advantageous as it reduces the likelihood of suchoff-target effects.

Ultimately, the modular nature of the Tri-TAC technology allows muchmore sophisticated fine tuning of the T-cell activation process. Forexample, the recruitment of the TCR complex could be modulated byengineering Tri-TAC molecules with a lower CD3 affinity. This could beused to mimic the natural low TCR affinity (Chervin et al., 2009) whileretaining a high affinity targeting domain to detect cancer targets.Unlike the classical CAR, the Tri-TAC technology can be engineered tomore closely resemble this.

In conclusion, the presented Tri-TAC technology is a highly efficientmolecular tool that is able to (1) efficiently trigger T-cell activationand cytotoxicity, (2) is able to do this by mimicking natural T-cellactivation and (3) does not require activation domains of its own.

Example 2. Characterization of the Tri-TAC Technology

An overview of the Tri-TAC technology is provided in FIG. 5.

FIG. 5A shows an example of CD8 T-cell activation based on theco-assembly of different receptors and their associated proteinpartners. Initially, the major histocompatibility complex I ispresenting an antigen (helix). This is recognized by a T cell receptor(TCR) complex capable of binding the antigen. The TCR complex containsseveral individual subunits. The α/β domains are able to interactdirectly with the antigen presented on MHC-I. The α/β domains theninteract with several other domains (ε, γ, δ, and ζ all of whichparticipate in T-cell activation via various intracellular activationdomains. The TCR complex interacts with MHC-I concurrently with the CD8co-receptor. The CD8 co-receptor binds to the MHC-I in an antigenindependent manner. CD8 directly interacts with Lck, a protein kinaseimportant for activating the TCR receptor complex. The CD8 and Lckinteraction also ensures their association with lipid rafts (membraneportion) microdomains, which are hypothesised to organize andencapsulate other relevant signalling moieties (dark spheres). Laterstages of activation then lead to CD28 recruitment. If this interactioncascade occurs several times in parallel, T-cells become activated andare able to exert their cytotoxic effects.

FIG. 5B provides an overview of Chimeric Antigen Receptors (CAR). CARsseek to reproduce the complex mechanism of T-cell activation bycombining several key activation domains, such as ζ and CD28, in asingle synthetically engineered molecule. The CAR then directlyinteracts with an antigen of choice using specific binding domains.Depicted here is an ankyrin repeat protein (DARPin). It is believed thatseveral such interactions occurring in parallel lead to T-cellactivation.

FIG. 5C depicts bispecific T-cell engager (BiTE) like molecules whichengage T-cells by directly cross linking the TCR complex to an antigenof choice. The BiTE like molecule depicted here contains two bindingdomains. The DARPin moiety is interacts with the target antigen. Thesingle chain variable fragment domain (scFv) binds the TCR complex viaits epsilon domain. Several such crosslinkings occurring in parallellead to T-cell activation.

FIG. 5D is an overview of the TAC technology mimicking the naturalactivation process. The T-cell Antigen Coupler (TAC) is able to bind toits antigen via the DARPin binding domain. DARPin is then linked to ascFv able to bind the epsilon domain of the TCR complex. The TAC thenassociates with the CD4 transmembrane and cytosolic domain. CD4, likeCD8, interacts with Lck and is situated in lipid rafts. Thus, TACscombine TCR recruitment with co-receptor stimulation. Without beingbound by theory, it is believed that several such interactions happeningin parallel lead to T-cell activation.

Different configurations of the TAC molecule are possible. FIG. 6A showsa model of the TAC molecule in configuration 1. The CD4-tail, 5transmembrane, and linker domains are combined with the TCR-epsilonspecific scFv (UCHT1). The scFv is then linked to the antigen bindingdomain. This domain is exchangeable. In this proposal the antigenbinding domains used are either a scFv or DARPin domain specific for theHer2 antigen. FIG. 6B shows a TAC molecule in configuration 2. Here, theCD4 domains first interact with the antigen binding domain. This domainis then linked to the TCR recruiting scFv (UCHT1) domain.

FIG. 7 shows the functionality of scFv CD4 TAC. FIG. 7A is a histogramshowing surface expression of the scFv CD4 TAC receptor relative toempty vector. Cells were stained using an FcHer2 antigen, which was inturn detected using fluorescently labelled antibodies. FIG. 7B showsantigen specific activation of T-cells expressing either the scFv CD4TAC (top) or scFV CAR (bottom). T-cells expressing either the scFv CD4TAC (top) or scFv CAR (bottom) were incubated with plate bound Her2antigen. Both modified cells showed antigen specific activation. TheDMSO negative control showed no activity (Data not shown). FIG. 7C showscomparable killing of MCF-7 human tumour cell line (Her2 positive) byboth scFv CD4 TAC and scFv CAR. Both scFv CD4 TAC and scFv CAR wereincubated with MCF-7 human tumour cell line (Her2 positive) and comparedto an empty vector control.

FIG. 8 is a characterization of CD4-TAC configuration 2. FIG. 8A is ahistogram of DARPin CD4-TAC configuration 2 relative to vector control.Surface expression was probed with the FcHer2 modified antigen. Cellsexpressing CD4-TAC configuration 2 show a distinct increase in FcHer2binding demonstrating high surface expression of the receptor. Forclarity the model of CD4 TAC configuration 2 is shown. FIG. 8B showsT-cells engineered with DARPin TAC configuration 2 exposed to platebound Her2 antigen. Cytokine production and degranulation were measured.Data show that DARPin TAC configuration 2 is a functional receptor.Treatment without antigen showed no T-cell activation (data not shown).FIG. 8C shows growth of CD4 TAC configuration 2 relative to empty vectorcontrol. Cells were grown in 100u/ml IL2 10 ng/ml IL7. Starting with100,000 cells, growth was monitored by counting culture samples atpredetermined intervals. Configuration 2 has a marked reduced growthrate relative to control.

FIG. 9 shows the functionality of DARPin CD4 TAC configuration 1. FIG.9A shows surface expression of DARPin CD4 TAC (red) compared to DARPinCAR (green), and the NGFR only control (blue). Cells were probed withreceptor specific antigen FcHer2. Histogram shows that DARPin CD4 TAC isexpressed well on the surface. However, its maximal surface expressionis lower compared to the CAR construct. FIG. 9B shows growth of CD4 TACconfiguration 1. For two weeks culture growth was monitored by samplingand manually counting cells. The empty vector shows similar growth asDARPin CAR. However TAC has reduced growth by comparison. FIGS. 9C and9D show the percentage of cells positive for various activation anddegradation markers. Empty vector, DARPin CD4 and DARPin CAR wereincubated with either plate bound antigen Her2 or DMSO control. Theresults of three separate experiments are summarized using thestatistical analysis software SPICE. The scatter graph shows thepercentage of cells positive for a set of activation markers. CD4-TACshow a higher percentage of cells, positive for degranulation markers.DARPin CAR cells are positive for a variety of activation markers withno significantly enriched population of degranulation markers. The piechart represents the same data. It demonstrates that CD4-TAC has amarkedly higher population of cells focused on degranulation. CD4-TAChas a majority of activated cells degranulate with various levels ofcytokine production. However, CARs show a more randomly distributedpattern of activation with degranulation constituting less than 50% ofthe total population. The pattern may be indicative of a less controlledT-cell activation by CARs.

FIG. 10 shows cytotoxicity and overall activity of TAC and CAR. Cellsengineered with either TAC, CAR or empty vector control were incubatedwith various human tumour cell lines. MDA MB 231, SK OV 3 and A549 allexpress the Her2 antigen. LOXIMVI is Her2 negative. It was observed thatin all cases, TAC shows enhanced cytotoxicity. The antigen negative cellline LOCIMVI is not being targeted, supporting that cytotoxicity isantigen specific.

FIG. 11 shows receptor surface expression and activation of various TACcontrols. Cell surface expression (left), degranulation (middle) andcytokine production (right) is shown in FIG. 11A. Constructs lackingspecific domains were made to determine the significance of thesedomains. From top to bottom the following domains were removed: DARPinantigen binding domain and UCHT1 TCR binding domain, with the fulllength TAC being at the bottom. Surface expression of TAC without theUCHT1 domain resulted in enhanced surface expression relative to fulllength CD4 TAC. The DARPin negative mutant could not be detected usingFcHer2 antigen. Degranulation (middle) was only observed in full lengthTAC. Both UCHT1 and DARPin deletion resulted in no degranulation.Similarly, cytokine production was only observed in the full length TAC.FIG. 11B shows the mouse cell line D2F2 was engineered to express thehuman Her2 antigen (D2F2/E2). Both cell lines were incubated withT-cells engineered with full length CD4-TAC or its deletion variants.The data show the Effector to Target ratio 4:1 endpoint. Only fulllength CD4-TAC was able to elicit a cytotoxic response. Thisdemonstrates that DARPin and UCHT1 domains are involved in receptorfunction.

FIG. 12 shows properties of various transmembrane TAC variants. FIG. 12Ais an overview of the various transmembrane constructs. The first set ofvariants is lacking the cytosolic domain. The CD4 TAC-cytosol has theentire cytosolic domain removed. The synthetic construct has the CD4 TMreplaced by a designed, highly hydrophobic membrane domain. Theglycophorine variant replaces the CD4 transmembrane domain with theglycophorine transmembrane domain. The GPI anchor variant uses the CD48GPI signal sequenced to attach the TAC to the membrane using the GPIanchor. The CD8A TAC variant replaced the transmembrane and cytosolicCD4 domain with the CD8a counterpart. FIG. 12B shows CD8 purifiedT-cells were engineered with the various constructs. Surface expressionof the various receptors relative to full length TAC is shown. All datais relative to the median fluorescent intensity of the control. Allvariants have a significantly lower receptor surface expression comparedto the full length CD4-TAC. The GPI anchor TAC variant is not detectableabove background. FIG. 12C depicts testing of the different variants fordegranulation and cytokine production. Cells were incubated with platepound Her2 antigen. The activity is presented as percent of cellspositive for either the degranulation maker CD107a (left bar graph) orthe percent of all cytokine producing cells taken together (TNFα, IFNgand TNFα/IFNg, right bar graph). GPI anchored or CD8a variants showbackground levels of degranulation and cytokine production.Glycophorine, synthetic and -cytosol TAC variants show a moderate levelof degranulation and a low level of cytokine production. In all casesthe activity is well below full length CD4-TAC. Taken together thisshows that anchoring TAC without its cytosolic domain leads tofunctional receptors with diminished activity.

FIG. 13 shows Lck interaction with TAC variants. In FIG. 13A, Her2antigen was covalently attached to magnetic beads. 293TM cells wereengineered to express both the TAC and TAC cytosolic deletion variant aswell as Lck. Beads were incubated with cell lysates over night andsubsequently washed and western blotted. Lck was detected using an Lckantibody, TACs were detected via Myc antibody. B-Actin was used ascontrol. b-Actin was not pulled down and only detected in thesupernatant (S). However both full length TAC and cytosolic deletionwere efficiently pulled down and detected in the pellet fraction (B).Vector control and TAC without cytosolic domain show comparable levelsof background Lck signal. Full length CD4 TAC however shows asignificant level of Lck relative to the total amount. FIG. 13B showsdensitometry analysis of the Lck detected in the pellet. Signal wascorrected relative to the negative control. This data supports that Lckis able to interact with full length CD4-TAC.

In FIG. 14, CD4 TAC surface expression and activity is compared to aBiTE like variant. FIG. 14A shows NGFR only control (left), CD4 TAC(middle) and BiTE like variant (right). Surface expression was testedusing the transduction marker NGFR and the Her2 antigen. TAC shows muchlower surface expression compared to BiTEs. Most notably, BiTE seems tosecrete enough coupling antibody to enable transduction negative cells(NGFR-) to show strong receptor expression. Both cytokine production anddegranulation are higher in BiTE like cells compared to TAG engineeredcells. FIG. 14B compares cytotoxicity in various Her2 positive celllines (MDA MB 231, SK OV 3, A549). In contrast to cytokine production,TAG engineered cells show significantly enhanced cytotoxic activity.

FIG. 15 shows comparison of CD4 TAG WT to a random mutagen library ofUCHT1. To test the ability to change TAG properties, 24 amino acidsfound on the binding surface of UCHT1 and TCR epsilon were individuallymutated. This gives rise to a theoretical number of 480 unique clones,all of which should be represented in this random library. FIG. 15Ashows the schematic representation of the mutant. Markings indicate themutations which are all in the scFv-epsilon interface. Figure FSB is ahistogram of surface expression. Engineered cells were probed withFcHer2 antigen to detect surface expressed receptor. The library shows amuch enhanced surface expression of the receptor. FIG. 15C shows WT andLibrary CD4 TAG cells incubated with plate bound antigen. Their abilityto activate and produce cytokines is presented. The library has similaractivity compared to the WT. Without being bound by theory, thissupports the idea that expression properties of TAG can be improvedwhile retaining the original functional profile by altering the scFvdomain.

FIG. 16 shows enhanced surface expression of the A85V, T161P mutant. Thelibrary was propagated for an extended period of time to select formutants with a growth advantage over the WT. A selected mutant wasanalysed (A85V, T161P; numbering is based on the UCHT1 domain fragment).FIG. 16A shows peripheral blood mononuclear cells (PBMC) were engineeredwith either WT CD4-TAC or the A85V, T161P mutant. The final CD4/CD8populations between CD4 TAG (left) and A85V, T161P mutant (right) arecompared. Notably, WT CD4-TAC leads to a reduced population of CD4positive cells. This effect is not observed in the mutant cells. FIG.16B shows surface expression, as determined by NGFR transduction makerand FcHer2 positivity, and indicates enhanced surface expression of theA85V, T161P mutant. FIG. 16C shows that A85V, T161P mutant cytokineproduction is diminished (DMSO controls showed no activity, data notshown). Degranulation between WT TAC and A85V, T161P mutant iscomparable.

FIG. 17 shows A85V, T161P mutant cytotoxicity and growth. In FIG. 17A,T-cells engineered with WT CD4 TAC and A85V, T161P mutant were incubatedwith the Her2 antigen positive cell lines SK OV 3, MDA MB 231 and A549.In all cases, the mutant displayed a reduced level of cytotoxicity; inthe case of A549, no cytotoxicity was detected. In FIG. 17B, cell growthin culture starting with 100 000 cells was monitored over 2 weeks.Periodically samples were taken and cells were counted manually. TheA85V, T161P mutant exhibits markedly improved growth compared to the WTvariant. Taken together, this demonstrates that the library is likely tocontain various mutants that enable the modification and optimization ofseveral TAC functions. Thus, UCHT1 can be used as a functionalmodulator.

While the present application has been described with reference to whatare presently considered to be the preferred examples, it is to beunderstood that the application is not limited to the disclosedexamples. To the contrary, the application is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

All publications, patents, and patent applications are hereinincorporated by reference in their entirety to the same extent as ifeach individual publication, patent or patent application wasspecifically and individually indicated to be incorporated by referencein its entirety.

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SEQUENCE LISTING

The instant application contains a Sequence Listing which has beensubmitted electronically in ASCII format and is hereby incorporated byreference in its entirety. Said ASCII copy, created on Aug. 21, 2019, isnamed 55247702301_SL.txt and is 30,993 bytes in size.

The invention claimed is:
 1. A B-cell maturation antigen (BCMA) T cellAntigen Coupler (BCMA-TAC), comprising: a) a first antigen bindingdomain polypeptide which binds BCMA; b) a second antigen binding domainpolypeptide that binds a CD3 epsilon protein associated with a TCRcomplex on the T cell; and c) a T cell co-receptor domain polypeptidecomprising a CD4 cytosolic domain and a CD4 transmembrane domain;wherein the components (a), (b) and (c) are fused directly to each otheror joined by at least one linker, and provided that the BCMA-TAC doesnot comprise a co-stimulatory domain.
 2. The BCMA-TAC of claim 1,wherein the first antigen binding domain polypeptide is a scFv.
 3. TheBCMA-TAC of claim 1, wherein the second antigen binding domainpolypeptide comprises an amino acid sequence having at least 99%identity to the amino acid sequence as set forth in SEQ ID NO:
 14. 4.The BCMA-TAC of claim 1, wherein the second antigen binding domainpolypeptide comprises the amino acid sequence as set forth in SEQ ID NO:14.
 5. The BCMA-TAC of claim 1, wherein the T cell co-receptor domainpolypeptide comprises an amino acid sequence having at least 99%identity to the amino acid sequence as set forth in SEQ ID NO:
 18. 6.The BCMA-TAC of claim 1, wherein the T cell co-receptor domainpolypeptide comprises the amino acid sequence as set forth in SEQ ID NO:18.
 7. A T cell expressing a BCMA-TAC according to claim
 1. 8. Apharmaceutical composition, comprising the T cell of claim 7, and acarrier.
 9. A method of treating a BCMA-expressing cancer in anindividual in need thereof, the method comprising administering thepharmaceutical composition of claim 8 to the individual, therebytreating the BCMA-expressing cancer.